📝 Added sandbox (code sketchbook)

sandbox/dup.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+int main() {
+    int file_desc = open("dup.txt", O_WRONLY | O_APPEND);
+
+    if (file_desc < 0)
+        printf("Error opening the file\n");
+
+    int copy_desc = dup(file_desc);
+
+    /* NOTE what is happening here, the dup() call creates a secondary
+     * file descriptor that duplicates the file descriptor
+     * (original: file_desc, copy: copy_desc),
+     * but references the same file (i.e. dup.txt) */
+
+    write(copy_desc, "This will be output to the file named dup.txt\n", 46);
+    write(file_desc, "This will also be output to the file named dup.txt\n", 51);
+
+    return 0;
+}